The present invention is directed to a method of manufacture of foam core panels having improved sound absorption capabilities. The present invention is further directed to the panels produced using this method, especially vehicle trim panels.
The inventions disclosed herein have particular applicability to the manufacture of interior trim panels for use in motor vehicles using polyurethane foam core panels manufactured with equipment having moving and/or stationary belts, platens, and/or molds which control the foam core thickness. Such panels may also be used as ceiling and wall panels for buildings as well as interior components for motor vehicles.
It is known in the art to manufacture composite structures having a semirigid polyurethane foam core using a combination of moving and/or stationary belts, platens, and/or molds which control the foam core thickness by restricting the total free-rise foaming of the selected chemical composition. The use of this method tends to create a foam core having increased density at the upper and lower portions and decreased density at the center portion. This density variation results in a closed cellular structure of relatively large size in the center portion creating a less dense portion and a closed cellular structure at or near the surfaces including the top and bottom portions having a smaller cell size creating a more dense portion. The smaller cell structure at the surfaces is due to the restriction impeding the free-rise foaming of the chemical composition created by the belts, platens, or molds being preset to uniformly control the entire panel thickness.
It is known that polyurethane foam composites having increased density and closed cellular structures do not exhibit the best sound absorption characteristics, and that increased sound absorption ability is desired in some applications. The methods used to increase the sound absorption capability of such foam composites include creating perforations or depressions into or through the surface of the composite structure or to laminate thereto additional materials that exhibit improved sound absorption characteristics.
Another method of manufacture of polyurethane foam composite structures is to form foam buns and thereafter to trim off the densified exterior surfaces. This trimmed bun is then cut to the desired end part thickness and thereafter secondary bonding of reinforcement and decorative cover materials is made to the shaped bun. The products manufactured using these methods may or may not be aesthetically appealing and are somewhat costly to manufacture.
The herein invention is directed towards using a current state of the art process for manufacturing a thermoformable semirigid polyurethane foam and thereafter skiving the panel produced through a center portion having a large cell structure to create two distinct panels each having one surface with a large cell structure, and said surface additionally including cells that have been cut open. Hence, a surface having increased sound absorption characteristics is provided on two foam panels which are made simultaneously from a single panel originating from a conventional process.